Primary carcinoma of the liver is one of common malignant tumors. About 260,000 new cases are diagnosed each year, which is approximately 4% of all cancer types. In recent years, the incident rate is increasing and this affects our health significantly. Thus, seeking advanced techniques for diagnosis and treatment of liver cancer have become more important.
There are various types of treatment for liver cancer. The main treatments include surgery, embolization, injecting alcohol into the tumor, injecting acetic acid into the tumor, microwave ablation, cryotherapy, chemotherapy, radiotherapy, immunotherapy, and supportive therapy. According to hepatocellular carcinoma therapeutic guideline of American Association for the Study of Liver Diseases, early treatment of patients is effective. Patients can be cured by surgery and tumor ablation. The 5-year survival rate is 50%-75%. Patients in the intermediate stage can only accept embolization, and the 3-year survival rate is 50%. At late stage, the 1-year survival rate drops to 50% or even lower.
What makes liver cancer so deadly? The liver tumors are growing quickly and typically diagnosed in the intermediate stage or late stage. In late stage cases, there is a significantly decreased treatment effect. Yet once late-stage patients are treated by a target therapy, their survival time is increased, the risk of death is reduced and the life quality is improved.
Lipiodol is an iodinated ester derived from poppy seed oil, and it is concentrated and selectively retained in hepatic tumor cells. Transcatheter infusion of Lipiodol via the hepatic artery has been used increasingly for diagnosis and treatment of hepatic cancers. Even tiny malignant tumors have been detected. Thus Lipiodol has a great potential as a carrier for chemotherapeutic or radiotherapeutic agents for targeted therapy.
Recently targeted therapy drugs have been broadly applied to cancer treatment. Targeted therapy blocks the growth of cancer cells by interfering with specific targeted molecules involved in carcinogenesis, tumor growth or repair processes such as cell transformation, proliferation or metastasis. The drugs can also inhibit tumor angiogenesis or block tumor nutrient supply so as to inhibit growth, accelerate apoptosis and prevent cancer spreading. The specific targeted molecules include tumor enzymes, small molecules in tumor cells, and antigens on tumor cell surfaces. Compared with conventional chemotherapy, targeted therapy is highly-selective and with much fewer side effects.
Rhenium-188 (188Re) is a radionuclide that emits beta and gamma rays, and having a half life of 16.9 hours. It is produced in a nuclear reactor and is convenient to use. The radiant energy and the half life of 188Re are optimal for disease diagnosis and treatment so that 188Re is a medical radioisotope with great potential in internal radiation therapy. Therefore 188Re-labeled Lipiodol ([188Re]-Lipiodol) is considered as a potential radiopharmaceutical agent for treatment of liver tumors.
If a precursor for labeling therapeutic agents is highly soluble in Lipiodol and is having selective retention property of Lipiodol in hepatic carcinoma tissues, it provides great help in treatment of liver cancer.